A top public security official in China’s resource-rich region of Inner Mongolia killed himself on Thursday, just days after two of his former colleagues were taken away for investigation by anti-corruption officials.

In a one-sentence report the same day, state-run Xinhua news agency said Li Zhibin, 51, deputy head of Inner Mongolia’s Public Security Department and chief of public security in the regional capital of Hohhot, took his own life.

The report did not say what prompted the death but on Friday Inner Mongolia’s official news website reported that Li left a suicide note saying he had been suffering from depression.

A senior Chinese law enforcement veteran familiar with the situation told the South China Morning Post that Li’s death was related to the corruption investigations.

“Inner Mongolia has been a main target of the nation’s anti-corruption effort and recently we have seen many officials taken away for investigation, especially in the law enforcement agencies,” the source said.

On Monday, Inner Mongolia’s Communist Party disciplinary watchdog announced that Du Baojun, deputy director of public security in Hohhot, had been detained for investigation.

Du worked with Li for two years at the Baotou public security bureau and again in Hohhot after Li was transferred to the regional capital.

The same watchdog announced on Tuesday that Meng Jianwei, deputy director of public security in Inner Mongolia, had also been detained for investigated. Meng was Li’s superior in Baotou from 2003 to 2009.

Inner Mongolia’s law enforcement system has been plagued by corruption and scandal. As chief of police in Chifeng, Li was part of the task force investigating the case of Zhao Liping, Inner Mongolia’s former top cop, who murdered a woman he had an affair with. Zhao was later sentenced to death.

If you or someone you know are having suicidal thoughts, help is available. For Hong Kong, dial +852 2896 0000 for The Samaritans or +852 2382 0000 for Suicide Prevention Services. In the US, call The National Suicide Prevention Lifeline on +1 800 273 8255.